Affecting more than one million Americans each year, skin cancer is the most prevalent form of cancer, accounting for nearly half of all new cancers reported, and the number is rising. However, according to the American Academy of Dermatology, most forms of skin cancer are almost always curable when found and treated early. For further details, see A. C. Geller et al., “The first 15 years of the American Academy of Dermatology skin cancer screening programs: 1985-1999,” Journal of the American Academy of Dermatology 48(1), 34-41 (2003), the entire contents of which are hereby incorporated by reference herein. As the number of subjects diagnosed with skin cancer continues to rise year-by-year, early detection and delineation are increasingly useful.
During a conventional examination, dermatologists visually survey the skin for lesions or moles that fit certain pre-defined criteria for a potential malignant condition. If an area is suspect, the doctor will perform a biopsy, sending the tissue to a pathology lab for diagnosis. Though effective, this method of detection is time consuming, invasive, and does not provide an immediate definitive diagnosis of a suspect lesion. It is also vulnerable to false positives which introduce unnecessary biopsy and associated costs. More importantly, early detection is very difficult at best, as developing cancers are not usually visible without close inspection of the skin.
Medical imaging has the potential to assist in the detection and characterization of skin cancers, as well as a wide variety of other conditions.
Hyperspectral medical imaging is useful because, among other things, it allows information about a subject to be obtained that is not readily visible to the naked eye. For example, the presence of a lesion may be visually identifiable, but the lesion's actual extent or what type of condition it represents may not be discernable upon visual inspection, or for that matter whether the lesion is benign or cancerous. Although tentative conclusions about the lesion can be drawn based on some general visual indicators such as color and shape, generally a biopsy is needed to conclusively identify the type of lesion. Such a biopsy is invasive, painful, and possibly unnecessary in cases where the lesion turns out to be benign.
In contrast, hyperspectral medical imaging is a powerful tool that significantly extends the ability to identify and characterize medical conditions. “Hyperspectral medical imaging” means utilizing multiple spectral regions to image a subject, e.g., the entire body or a body part of a human or animal, and thus to obtain medical information about that subject. Specifically, each particular region of a subject has a unique spectral signature extending across multiple bands of the electromagnetic spectrum. This spectral signature contains medical, physiological, and compositional information about the corresponding region of the subject. For example, if the subject has a cancerous skin lesion, that lesion may have a different color, density, and/or composition than the subject's normal skin, thus resulting in the lesion having a different spectrum than the normal skin. While these differences may be difficult to visually detect with the naked eye, the differences may become apparent through spectroscopic analysis, thus allowing the lesion (or other medical condition resulting in a measurable spectroscopic feature) to be identified, characterized, and ultimately more readily treated than would be possible using conventional visual inspection and biopsy. Such spectral differences can be presented to a user (such as a physician), for example, by constructing a two-dimensional image of the lesion. See, for example, U.S. Pat. No. 6,937,885, the entire contents of which are hereby incorporated by reference.
However, the potential applicability of conventional systems and methods for hyperspectral medical imaging has been limited by the types of sensors and analytical techniques used. What are needed are more powerful and robust systems and methods for collecting, analyzing, and using hyperspectral information to diagnose and treat subjects.